1. Field of the Invention
The present invention relates to a conveyance system for use in conveying articles in a machine tool loader, an industrial machinery or a physical distributing machine and, more particularly, to a conveyance system including at least one curved section in the path of conveyance.
2. Description of the Related Art
As a conveyance system for delivering or discharging workpieces in or from a machine tool such as, for example, a lathe or turning machine, the type has been well known, which includes a lifter, mounted on a traveling member movable along a guide rail, and a chuck provided in a loader head at a lower end of the lifter to hold a workpiece. In this type of the conveyance system, the traveling member moves along a linear transport path. It has, however, been determined that only with the linear transport path, an installation space for a machine tool is limited and it is difficult to make the efficient utilization of the floor space available in a factory. Because of this, suggestions have been made to include at least one curved section in the transport path such as disclosed in, for example, JP Laid-open Patent Publication No. 04-283039 and JP Laid-open Patent Publication No. 2010-149269. Also, even in the industrial machinery, a similar suggestion has been made to include a curved section in the transport path.
In addition, a linear motor has been employed in, for example, a conveyor carriage employed in a physical distributing apparatus. While the linear motor is available in various types such as, for example, a linear induction motor (LIM), a linear synchronous motor (LSM) and a linear direct current motor, the linear induction motor is largely employed in a long distance conveyance system. A main stream of this linear synchronous motor is of a type including magnets, installed on the ground side, and a coil side installed movably.
The example, such as disclosed in the JP Laid-open Patent Publication No. 2007-82307, has been suggested in which primary coils of the linear synchronous motor system are partially discretely arranged on the ground side in, for example, a curved section or sections proximate to opposite ends of the transport path where acceleration and deceleration are required. However, the linear synchronous motor system utilized in such a case is merely utilized in an auxiliary manner at the curved section or such sections proximate to the opposite ends of the transport path, and the linear induction motor is mainly utilized even in such a case.